ML031040010
| ML031040010 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 04/09/2003 |
| From: | Katz P Constellation Energy Group |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| EA-03-009, TAC MB7752, TAC MB7753 | |
| Download: ML031040010 (11) | |
Text
Peter E. Katz 1650 Calvert Cliffs Parkway Vice President Lusby, Maryland 20657 Calvert Cliffs Nuclear Power Plant 410 495-4455 Constellation Generation Group, LLC 410 495-3500 Fax Constellation v wEnergy Group April 9, 2003 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318 Supplemental Data for Request for Relaxation from Certain Inspection Requirements in NRC Order (EA-03-009) for Reactor Pressure Vessel Head Penetration Nozzles (TAC Nos. MB7752 and MB7753)
REFERENCES:
(a) Letter from Mr. P. E. Katz (CCNPP) to Document Control Desk (NRC),
dated February 18, 2003, Response to Issuance of Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors (b) Letter from Mr. P. E. Katz (CCNPP) to Document Control Desk (NRC),
dated March 13, 2003, Response to Request for Additional Information Regarding Interim Inspection Requirements for Reactor Pressure Vessel Head (TAC Nos. MB7752 and MB7753)
(c) Letter from Mr. P. E. Katz (CCNPP) to Document Control Desk (NRC),
dated April 4, 2003, Response to Request for Additional Information Regarding Interim Inspection Requirements for Reactor Pressure Vessel Head (TAC Nos. MB7752 and MB7753)
(d) Letter from Mr. S. J. Collins (NRC) to Holders of Licenses for Operating Pressurized Water Reactors, dated February 11, 2003, Issuance of Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors (EA-03-009)
By letter dated February 18, 2003 (Reference a) and supplemented by letters dated March 13, 2003 and April 4, 2003 (References b and c), Calvert Cliffs Nuclear Power Plant, Inc. submitted a request for relaxation from the inspection requirements of Section IV.C(l)(b)(i) of Order EA-03-009 (Reference d).
Calvert Cliffs Nuclear Power Plant completed the inspections required by Reference (d) on April 8, 2003.
This letter supplements our relaxation request by providing the final results of our ultrasonic testing examination and a response to Nuclear Regulatory Commission Staffs April 8, 2003, verbal request for additional information. This letter also requests additional relaxation from the Order due to instrument limitations encountered during the inspection.
Document Control Desk April 9, 2003 Page 2 Our response to the Staffs request for additional information and the final Reactor Pressure Vessel Head control element drive mechanism penetrations' ultrasonic testing examination results, including the specific nozzles for which relaxation is requested by Reference (a), are contained in Attachment (1). The additional relaxation request is contained in Attachment (2).
Calvert Cliffs Nuclear Power Plant, Inc. requests approval of the relaxation requests by April 18, 2003, the current scheduled date for Calvert Cliffs Unit 2 startup.
Should you have questions regarding this matter, we will be pleased to discuss them with you.
PEK/JKK/bjd Attachments: (1) Response to Request for Additional Information and Reactor Pressure Vessel Head UT Examination Results (2) Additional Relaxation Request cc: J. Petro, Esquire H. J. Miller, NRC J. E. Silberg, Esquire Resident Inspector, NRC Director, Project Directorate I-l, NRC R. I. McLean, DNR G. S. Vissing, NRC
ATTACHMENT (1)
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION AND REACTOR PRESSURE VESSEL HEAD UT EXAMINATION RESULTS Calvert Cliffs Nuclear Power Plant, Inc.
April 9, 2003
ATTACHMENT (1)
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION AND REACTOR PRESSURE VESSEL HEAD UT EXAMINATION RESULTS NRC Request:
Provide the bounding hoop and axial stresses present at the location of lowest coverage above the J-groove weld.
CCNPP Response:
The requested information is provided on Figure 1 below. The bounding value is located on Nozzle 43 which had coverage to 0.95 inches above the root of the J-groove weld. Nozzle 43 has a 38.5 degree angle with the head. Calculated stresses are reported for a 42.5 degree nozzle, which bounds a 38.5 degree nozzle. Stresses are provided at three locations: on the outside diameter (OD) at the elevation of highest coverage, on the inside diameter (ID) at the same elevation, and on the ID at the elevation of highest coverage. Coverage elevations above the J-groove weld have been reported for coverage on the OD. In all cases coverage on the ID is higher. This is due to the configuration of the transducers in the blade probe and is analogous to the situation at the bottom of the nozzle (see Figure 1 in Attachment 2). Further discussion on the configuration of the transducers in the blade is contained in Attachment (2).
FIGURE 1 Bounding hoop and axial stresses at elevation of minimum coverage extent above the root of the J-groove weld occurs on Nozzle 43 0.95 inches above weld 1.38 inches above weld 0.95 inches above weld on nozzle ID on nozzle ID on nozzle OD Hoop stress (ksi) = 37.5 Hoop stress (ksi) = 27.4 Hoop stress (ksi) = -10.5 Axial stress (ksi) = 14.9 Axial stress (ksi) = 8.3 Axial stress (ksi) = -15 I
I -0.43 inch Actual extent above J-groove weld on ID surface equals -1.38 inch Minimum axial coverage 0.95 inches above J-groove weld root I I -1
- 1_____
1
ATTACHMENT (1)
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION AND REACTOR PRESSURE VESSEL HEAD UT EXAMINATION RESULTS Calvert Cliffs Nuclear Power Plant - Unit 2 Ultrasonic Testing Data Coverage Matrix for Control Element Drive Mechanism Nozzles CEDM Extent of UT Coverage in RVHP Nozzle Material UT Approximate Min ** Coverage Leak Path Indications/
Angle Distance Coverage Weld Below Assessment Leakage Pen Between Above Weld @ Weld Region Weld Deternination Path
- Nozzle and Weld Root Root Coverage Coverage Possible? Indications Head Root (Theta) (Theta) (Theta) (Theta) (Yes/No)
(Degrees) 1 0.000 2.0* 360 360 360 360 Yes No 2 11.143 1.6 360 360 360 360 Yes No 3 11.143 1.55 360 360 360 360 Yes No 4 11.143 1.85 360 360 360 360 Yes No 5 11.143 1.65 360 360 360 360 Yes No 6 11.976 2.11* 360 360 360 360 Yes No 7 11.976 1.40 360 360 360 360 Yes No 8 11.976 1.83 360 360 360 360 Yes No 9 11.976 1.4 360 360 360 360 Yes No 10 22.620 1.40 360 360 360 360 Yes No 11 22.620 1.9 360 360 360 360 Yes No 12 22.620 1.7 360 360 360 360 Yes No 13 22.620 1.45 360 360 360 360 Yes No 14 24.083 1.95 360 360 360 360 Yes No 15 24.083 1.70 360 360 360 360 Yes No 16 24.083 1.8 360 360 360 360 Yes No 17 24.083 2.12* 360 360 360 360 Yes No 18 25.514 1.45 360 360 360 360 Yes No 19 25.514 1.45 360 360 360 360 Yes No 20 25.514 1.45 360 360 360 360 Yes No 21 25.514 1.55 360 360 360 360 Yes No 22 25.514 1.65 360 360 360 360 Yes No 23 25.514 1.45 360 360 360 360 Yes No 24 25.514 1.7 360 360 360 360 Yes No 25 25.514 1.65 360 360 360 360 Yes No 26 29.275 1.55 360 360 360 360 Yes No 27 29.275 1.46 360 360 360 360 Yes No 28 29.275 1.82 360 360 360 360 Yes No 29 29.275 1.82 360 360 360 360 Yes No 30 29.275 1.75 360 360 360 360 Yes No 31 29.275 1.20 360 360 360 360 Yes No 32 29.275 1.5 360 360 360 360 Yes No 33 29.275 1.24 360 360 360 360 Yes No 34 34.875 1.43 360 360 360 360 Yes No 35 34.875 1.3 360 360 360 360 Yes No 36 34.875 1.45 360 360 360 360 Yes No 37 34.875 1.85 360 360 360 360 Yes No 38 38.501 1.30 360 360 360 360 Yes No 2
ATTACHMENT (1)
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION AND REACTOR PRESSURE VESSEL HEAD UT EXAMINATION RESULTS Calvert Cliffs Nuclear Power Plant -- Unit 2 Ultrasonic Testing Data Coverage Matrix for Control Element Drive Mechanism Nozzles CEDM Extent of UT Coverage in RVHP Nozzle Material UT Approximate Min ** Coverage Leak Path Indications/
Angle Distance Above Coverage Weld Below Assessment Leakage Pen Between Above Weld @ Weld Region Weld Determination Path
- Nozzle and Weld Root Root Coverage Coverage Possible? Indications (Degres Root (Theta) (Theta) (Theta) (Theta) (YesNo) 39 38.501 1.39 360 360 360 360 Yes No 40 38.501 1.37 360 360 360 360 Yes No 41 38.501 1.2 360 360 360 360 Yes No 42 38.501 1.2 360 360 360 360 Yes No 43 38.501 0.95 360 360 360 360 Yes No 44 38.501 1.05 360 360 360 360 Yes No 45 38.501 1.4 360 360 360 360 Yes No 46 41.795 1.3 360 360 360 360 Yes No 47 41.795 1.15 360 360 360 360 Yes No 48 41.795 1.50 360 360 360 360 Yes No 49 41.795 1.15 360 360 360 360 Yes No 50 41.795 1.2 360 360 360 360 Yes No 51 41.795 1.0 360 360 360 360 Yes No 52 41.795 1.3 360 360 360 360 Yes No 53 41.795 1.2 360 360 360 360 Yes No 54 42.510 1.2 360 360 360 360 Yes No 55 42.510 1.55 360 360 360 360 Yes No 56 42.510 1.80 360 360 360 360 Yes No 57 42.510 1.2 360 360 360 360 Yes No 58 42.510 1.25 360 360 360 360 Yes No 59 42.510 1.55 360 360 360 360 Yes No 60 42.510 1.2 360 360 360 360 Yes No 61 42.510 1.0 360 360 360 360 Yes No 62 42.510 1.25 360 360 360 360 Yes No 63 42.510 1.25 360 360 360 360 Yes No 64 42.510 1.35 360 360 360 360 Yes No 65 42.510 1.50 360 360 360 360 Yes No
- Relaxation from the Order requirement to inspect 2 inches above the J-groove weld is requested for all CEDM nozzles except for Nozzles 1, 6, and 17.
- Coverage is for nozzle outside diameter. Nozzle inside diameter coverage is 0.43 inches greater for all penetrations.
3
ATTACHMENT (2)
ADDITIONAL RELAXATION REQUEST Calvert Cliffs Nuclear Power Plant, Inc.
April 9, 2003
ATTACHMENT (2)
ADDITIONAL RELAXATION REQUEST RELAXATION REQUEST:
In accordance with Section IV.F(2) of Reference (1), Calvert Cliffs Nuclear Power Plant, Inc. (CCNPP) hereby submits a request for relaxation.
ORDER REQUIREMENT FROM WHICH RELAXATION IS REQUESTED:
Section IV.C(1)(b)(i) -- Ultrasonic testing (UT) of each Reactor Pressure Vessel (RPV) head penetration nozzle (i.e., nozzle base material) from two inches above the J-groove weld to the bottom of the nozzle.
The request for relaxation from the Order requirement for two inches above the weld for control element drive mechanism (CEDM) penetration was the subject of our original relaxation request (References 2, 3, and 4). This relaxation request is for missed examination coverage near the bottom end of the CEDM nozzles due to instrument limitation. (Note: This relaxation request applies only to CEDM nozzles. The incore instrumentation nozzles and vent line were inspected using a rotating probe that did not have the limitations described for the blade probe.)
SPECIFIC PENETRATION NOZZLES FOR WHICH RELAXATION IS REQUESTED:
This relaxation request applies to all Calvert Cliffs Nuclear Power Plant Unit 2 CEDM penetrations 1 through 65. The un-interrogated area at the bottom end of the CEDM nozzles is due to the configuration of the ultrasonic transducers in the probes used to examine the nozzles. These probes have separate transducers for sending and receiving the ultrasonic signal. The probes, used for detection of the most significant type of cracks, circumferential cracks, have the two transducers arranged one above the other.
The transducers used in the CE-type circumferential blade probe are located nominally 0.86-inch apart.
With this configuration, the lower transducer will not contact the inside wall on the nozzle until the upper transducer is inserted greater than approximately 0.86-inch into the nozzle. Since the scanning process requires that both transducers be in contact with the surface, the probe cannot scan a small portion of the bottom of the nozzle. Based on the geometry involved in the transducer location and nozzle configuration, the portion that cannot be scanned is the portion extending from the bottom of the nozzle upward for a distance of approximately 0.56-inch. The value is half the distance between the two transducers plus a 1/8-inch radius at the bottom corner of the nozzle. The actual volume of unobtainable coverage is triangular in cross-section. The inside diameter of the nozzle receives relatively complete coverage (with a lateral wave), while the UT angle defines a triangle hypotenuse extending from the nozzle inside diameter lower end, to a spot on the nozzle outside diameter, located approximately 0.56-inch above the bottom of the nozzle. The other legs of the triangle are the lower portion of the nozzle outside diameter and the bottom surface of the nozzle. Figure 1 illustrates the un-interrogated area.
JUSTIFICATION FOR RELAXATION REQUEST:
Compliance with the requirements specified in the Order would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Use of an additional, different type of probe would not provide information that is significant to preventing leakage or degradation of the reactor coolant system pressure boundary. Examination of the bottom of the nozzle could be accomplished by surface examination. However, this presents a significant hardship since our inspection vendor does not currently have the capability of performing eddy current examination for this application. The other alternative, dye penetrant examination, has prohibitive worker dose implications without a commensurate increase in quality or safety. Removal of thermal guide sleeves to provide access for a rotating probe has similar dose implications that presents hardship with no commensurate increase in safety or quality.
The UT coverage area achieved provides an acceptable level of quality and safety because the un-interrogated area involves a portion of the nozzle at the very bottom, below the J-groove weld. Below the 1
ATTACHMENT (2)
ADDITIONAL RELAXATION REQUEST J-groove weld, the nozzle is essentially an open-ended tube and the nozzle wall in this portion is not part of the Reactor Coolant System pressure boundary. To determine the significance of an axial flaw that is contained in the non-pressure boundary nozzle material in the un-interrogated region of the nozzle, a flaw tolerance approach was used. A flaw evaluation was performed postulating an axial flaw at the bottom of the nozzle. A through-wall flaw could grow approximately 0.376 inches vertically during an additional two years of operation. The distance below the weld scanned with UT techniques exceeded 0.4 inches for all CEDM nozzles, with no noticeable indications. Therefore, any crack below this region could not grow into the weld during the next two years of operations.
We conclude that our inspection results and analysis prove that no flaw can exist in the bottom portion of the nozzle that could grow to the weld during an additional cycle of operation. Therefore, there is no possibility of leakage from an undiscovered flaw in the region for which relaxation is sought.
The fracture mechanics evaluation was performed for nozzle material having 37.5 ksi yield strength, which is the yield strength for the two heats of material used to fabricate the Calvert Cliffs Unit 2 CEDMs. The residual and operating stresses used in the fracture mechanics analysis were calculated in a finite element model (FEM) of Calvert Cliffs CEDMs. The FEM assumed material yield strength of 42 ksi, which is bounding for both Calvert Cliffs Units. Since Unit 2 has lower yield strength material, the actual stresses will be slightly lower in Unit 2 as indicated in Reference (4). Lower applied stresses would result in lower crack growth rates. The stress distributions for the material below the weld was provided in Reference (3). The maximum hoop stress in the bottom portion of the nozzle (lowest 0.56 inch) is 25.5 ksi. This maximum hoop stress was used for the bounding evaluation of the hypothetical through-wall crack growth.
Flaw growth due to primary water stress corrosion cracking was assessed using the Materials Reliability Program (MRP) 75t percentile level curve (Reference 5). The MRP model provides a reference crack growth rate at 3250 C and uses an activation energy of 31,000 calories/mole to account for differences in operating temperature. We note that the Staff is still reviewing the crack growth rates provided in MRP-55. Should the Staff find the crack growth rate formula described in MRP-55 to be unacceptable, CCNPP would revise our analysis that justifies no examination of the bottom 0.56 inches of the nozzles.
The safety issues that are addressed by the inspections mandated by the Order are degradation (corrosion) of the low-alloy steel RPV head and ejection of the vessel head penetration nozzle due to circumferential cracking of the nozzle above the J-groove weld. The following three items provide reasonable assurance that these safety issues are addressed:
- 1. The bare-metal visual examination of CCNPP Unit 2 demonstrated the integrity of the RPV head and the absence of ongoing degradation of the head.
- 2. The analysis described above demonstrates that no flaw located in the bottom portion of the nozzle would propagate to a level adjacent to the weld within a two-year operating period.
- 3. The UT examination of 65 CEDM nozzles, 8 incore instrumentation nozzles, and 1 vent line in accordance with Section IV, Paragraph C.(1)(b)(i) of the Order (subject to relaxation of the requirement for examination of the very top and very bottom of the required inspection areas) reasonably demonstrates that the RPV head penetration nozzles are intact throughout the region of inspection. These examinations provide reasonable assurance that no circumferential cracking of the nozzles above the J-groove weld is present and no through-wall leakage or degradation of the RPV head should occur.
2
ATTACHMENT (2)
ADDITIONAL RELAXATION REQUEST CONCLUSION:
As described above, compliance with the Order requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. Therefore, in accordance with the provisions of Section IV.F(2) of the Order, we request relaxation of the requirement described in Section IV.C(l)(b)(i).
REFERENCES
- 1. Letter from Mr. S. J. Collins (NRC) to Holders of Licenses for Operating Pressurized Water Reactors, dated February 11, 2003, Issuance of Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors (EA-03-009)
- 2. Letter from Mr. P. E. Katz (CCNPP) to Document Control Desk (NRC), dated February 18, 2003, Response to Issuance of Order Establishing Interim Inspection Requirements for Reactor Pressure Vessel Heads at Pressurized Water Reactors
- 3. Letter from Mr. P. E. Katz (CCNPP) to Document Control Desk (NRC), dated March 13, 2003, Response to Request for Additional Information Regarding Interim Inspection Requirements for Reactor Pressure Vessel Head (TAC Nos. MB7752 and MB7753)
- 4. Letter from Mr. P. E. Katz (CCNPP) to Document Control Desk (NRC), dated April 4, 2003, Response to Request for Additional Information Regarding Interim Inspection Requirements for Reactor Pressure Vessel Head (TAC Nos. MB7752 and MB7753)
- 5. Materials Reliability Program (MRP) Crack Growth Rates for Evaluating Primary Water Stress Corrosion Cracking (PWSCC) of Thick-Wall Alloy 600 Material (MRP-55) Revision 1, EPRI Report, November 2002 3
ATTACHMENT (2)
ADDITIONAL RELAXATION REQUEST FIGURE 1 Illustration of the Un-interrogated Area at the Bottom of the CEDM Nozzles I~zzeZ1 I ozeboftorII 4